Well-Known Member

One of the more interesting cars I swapped engines in I tuned for more torque. I could let the clutch out at idle and it would move along at a walk. Hit the loud pedal and it would spin its wheels until around 35mph when it was time to change gear. That was a whopping 1108cc and maybe 50hp in a small 1990 car. One person borrowed and brought it back telling me it was an animal the way it responded to the throttle. It frightened his wife who usually drove a 2L car. On twisty back roads, it felt and moved very quickly. Straights, utterly hopeless. I could have given it more power instead of torque over a wide range, but it would have been a lot harder to drive quickly.
Modern engines have higher specific torque than older ones. But they often have lighter flywheels to help acceleration, that makes them unhappy at lower revs. There is a lot more to how cars feel than raw hp and torque numbers.
Fortunately, we don't need to bother with a wide torque range in planes and can shoot for high hp a specific RPM with no ill effects if the engine stays together.

Well-Known Member

I almost forgot: Aviation-specific cylinder heads for the VW. The best bang-for-the buck endeavor (IMO) for the US EAB community. The existing VW heads are good if you treat them right (temps! valve adjustments!), but the engine would benefit from heads purpose-built for aircraft use. Features:
-- Generous fins that are free of flash so the air really goes through the passages, especially near the exhaust valve
-- Valves that are smaller than those in the high-rpm heads used by the street racers. At our direct-drive 3600 RPM, there's no need for giant valves, and smaller ones leave more meat in the heats (so fewer cracks)
-- A smart location for the second plug so it can be easily changed AND is far enough away from the valves so it doesn't promote cracks
-- TimeSerts or other steel inserts inserted into the heads for the spark plugs to screw into. No more stripped plug holes.
-- A dedicated spot for the CHT thermocouple. There are several fine places on any of he existing heads, but there's no standardized agreeement on where to put them. Some folks put a ring under the spark plug, some folks tap a hole in a fin, some folks mount them under one of the studs--and al result in deiiferent readings. When Joe says his CHTs never get hotter than 350F, you need to ask him where te sensor is mounted. A tapped spot that all could use would help fix this.
-- For the smaller aviation VWs (1835cc and below?) -- all the above features, but with single port heads (for better charge velocity, VE, and torque at airplane RPMs)

Again, some of the existing heads work well, but these heads would do things a little better.

I think a single common camshaft for all the sections--pushrods to the 2 valves per cylinder. So, you'd need 6 different camshafts to cover 2,4,6,8,10,12 cylinder variants. >Perhaps< there would be a way to have a single camshaft that was one section long that could link to the next one , but I'd guess that would be troubleprone.

Well-Known Member

Yep, 61 cu inches to produce 75 HP = 1.23HP per cu inch. Wow, those "engineers" at Lycoming and Continental who can only make 0.5 (reliable) HP per cubic inch must be idiots. Those O-200's should be making 246 reliable HP, hour after hour. Imbeciles!

Well-Known Member

Yep, 61 cu inches to produce 75 HP = 1.23HP per cu inch. Wow, those "engineers" at Lycoming and Continental who can only make 0.5 (reliable) HP per cubic inch must be idiots. Those O-200's should be making 246 reliable HP, hour after hour. Imbeciles!

Well-Known Member

The old straight eights might be remembered fondly but they are inferior in almost every way to comparably sized modern engines. A 6L L96 puts out 340 lb./ft. at 2000 rpm, Packard 6L 330 at 2200. The L84 puts out 140 more hp on the top end and an LS3 (6.2L) puts out more than double the hp of the Packard (can do twice the amount of work per unit time and probably 3 times with proper gearing). The LS engines weigh about half of what these old straight 8s weigh. Fuel economy, longevity, emissions are all vastly superior. This is why the LS engines are looked at for aircraft. A 5L Ford Coyote puts out 400 lb./ft. at 3850 rpm. Dodge and Toyota 5.4L V 8s exceed 330 lb./ft at 2000 rpm as well.

The modern V6 turbo engines like the Ecoboost have staggering torque at low rpm- over 400 lb./ft. from 2000 rpm all the way to 4500 rpm- from only 3.5L and run on 87 octane. Rather impressive.

I am not talking about fuel economy, longevity, emissions. Just very low rpm torque performance in high gear on a steep hill.
I have never driven any of today's engines that will go down to 10-15 mph in high gear on a steep hill and when you shove the gas peddle down and accelerate as smoothly while picking up speed as those old heavy iron 8's.
My father and his 3 business pardners all drove Cords. I have driven the 37 Cord Hollywood Graham but wasn't allowed to drive the 37 Cord Conv with the Super Charged engine.

Guess I'm old fashion because I like old 1930's cars and round engine airplanes.

Attachments

Well-Known Member

If I could take an off the shelf motor and throw money at it I would get a small alloy block 4 cylinder motor and make an aviation specific head for it.
2 spark plug holes per cylinder.
2 valves per cylinder.
Reduction drive shaft running at 2 to 1 with bearings at front and rear to carry prop loads.
Secondary function of shaft is to activate valves.
For a 3 cylinder engine some balance factor built into shaft.
Now for the hard part.There has to be a drive system either belt or gear with some cushioning to drive the secondary shaft.

Well-Known Member

I almost forgot: Aviation-specific cylinder heads for the VW. The best bang-for-the buck endeavor (IMO) for the US EAB community. The existing VW heads are good if you treat them right (temps! valve adjustments!), but the engine would benefit from heads purpose-built for aircraft use. Features:
-- Generous fins that are free of flash so the air really goes through the passages, especially near the exhaust valve
-- Valves that are smaller than those in the high-rpm heads used by the street racers. At our direct-drive 3600 RPM, there's no need for giant valves, and smaller ones leave more meat in the heats (so fewer cracks)
-- A smart location for the second plug so it can be easily changed AND is far enough away from the valves so it doesn't promote cracks
-- TimeSerts or other steel inserts inserted into the heads for the spark plugs to screw into. No more stripped plug holes.
-- A dedicated spot for the CHT thermocouple. There are several fine places on any of he existing heads, but there's no standardized agreeement on where to put them. Some folks put a ring under the spark plug, some folks tap a hole in a fin, some folks mount them under one of the studs--and al result in deiiferent readings. When Joe says his CHTs never get hotter than 350F, you need to ask him where te sensor is mounted. A tapped spot that all could use would help fix this.
-- For the smaller aviation VWs (1835cc and below?) -- all the above features, but with single port heads (for better charge velocity, VE, and torque at airplane RPMs)

Again, some of the existing heads work well, but these heads would do things a little better.

Oh--and sell them for $100 each!

On the modular opposed water-cooled engine idea:

I think a single common camshaft for all the sections--pushrods to the 2 valves per cylinder. So, you'd need 6 different camshafts to cover 2,4,6,8,10,12 cylinder variants. >Perhaps< there would be a way to have a single camshaft that was one section long that could link to the next one , but I'd guess that would be troubleprone.

Agree 100% on the VW heads. Also could start getting a more HP with the heads taking care of the extra heat. Then the limit would be the mag case. A well balance engine does help on the case life. The aluminum case is 17 pounds heavier.

wasn't there someone in south america I think that built and was testing a set of heads they made specifically for aircraft use?? did a quick google search but cant seem to find it. this would have been a couple years back.

they do list "gross" hp.. which is amusing given that they are comparing to SAE hp.... which is again different than the automotive ratings....

Well-Known Member

wasn't there someone in south america I think that built and was testing a set of heads they made specifically for aircraft use?? did a quick google search but cant seem to find it. this would have been a couple years back.

they do list "gross" hp.. which is amusing given that they are comparing to SAE hp.... which is again different than the automotive ratings....